Optimization of extraction of functional protein hydrolysates from chicken egg shell membrane (ESM) by ultrasonic assisted extraction (UAE) and enzymatic hydrolysis

The objective of this study was to investigate the effects of ultrasonic pretreatment on the enzymatic hydrolysis of eggshell membrane (ESM) proteins and their functional properties. Response surface methodology (RSM) and Box-Behnken design were used to determine the optimal conditions for ultrasonic extraction. The optimum conditions obtained were amplitude, time and solid-to-solvent ratio of 95.74%, 28.06 min and 1:30 (g: mL) respectively. Ultrasonic pretreatment using the optimized conditions prior to enzymatic hydrolysis by alcalase and papain respectively resulted in increased protein concentration and degree of hydrolysis of the hydrolysates as compared to the control samples (untreated enzymatic hydrolysates) and also improved their functional properties. The hydrolysates obtained by ultrasonic pretreatment followed by alcalase hydrolysis demonstrated better solubility, emulsifying properties, foaming properties and water holding capacity as compared to the pretreated papain hydrolysates and the untreated hydrolysates. However, in comparison with control, the ultrasonic pretreatment did not significantly enhance the oil holding properties of the enzymatic hydrolysates. The improved functional properties of the hydrolysates demonstrate their potential use as functional and nutritional food ingredients in the food industries.